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Higher oxidation states of prostaglandin H synthase. Rapid electronic spectroscopy detected two spectral intermediates during the peroxidase reaction with prostaglandin G2.
- Source :
-
European journal of biochemistry [Eur J Biochem] 1988 Jan 15; Vol. 171 (1-2), pp. 321-8. - Publication Year :
- 1988
-
Abstract
- The reaction of prostaglandin H synthase with prostaglandin G2, the physiological substrate for the peroxidase reaction, was examined by rapid reaction techniques at 1 degree C. Two spectral intermediates were observed and assigned to higher oxidation states of the enzymes. Intermediate I was formed within 20 ms in a bimolecular reaction between the enzyme and prostaglandin G2 with k1 = 1.4 x 10(7) M-1 s-1. From the resemblance to compound I of horseradish peroxidase, the structure of intermediate I was assigned to [(protoporphyrin IX)+.FeIVO]. Between 10 ms and 170 ms intermediate II was formed from intermediate I in a monomolecular reaction with k2 = 65 s-1. Intermediate II, spectrally very similar to compound II of horseradish peroxidase or complex ES of cytochrome-c peroxidase, was assigned to a two-electron oxidized state [(protoporphyrin IX)FeIVO] Tyr+. which was formed by an intramolecular electron transfer from tyrosine to the porphyrin-pi-cation radical of intermediate I. A reaction scheme for prostaglandin H synthase is proposed where the tyrosyl radical of intermediate II activates the cyclooxygenase reaction.
Details
- Language :
- English
- ISSN :
- 0014-2956
- Volume :
- 171
- Issue :
- 1-2
- Database :
- MEDLINE
- Journal :
- European journal of biochemistry
- Publication Type :
- Academic Journal
- Accession number :
- 3123232
- Full Text :
- https://doi.org/10.1111/j.1432-1033.1988.tb13793.x